I think, but am not 100% sure, that until this very moment I have never felt kinship with a fruit fly.
I'm happy to add that while in these years of growing old I continue to feel stress and my responses seem no less diverse and no more or less effective than earlier in life, I no longer feel rejected by attractive females and am no longer tempted to drown my sorrows. My most reliable balm for dysphoria includes the gift of companionship and good conversation, the pleasures of reading, writing and long rambles in field and forest. That, I suppose, may still be regarded by neuroscientists as benign self-medication.
Lest you conclude that I am fruitcake and/or aspiring to publish in True Confessions (available only at supermarkets) the above reflection was prompted by reading a New York Times account of a study published in the leading American scientific journal, Science.
The study itself is entitled "Sexually Rejected Flies Turn to Booze." Well, perhaps that is the racier online version. I have not read the Science article. The illustration at right, however, is drawn from the version on the Science website. It's caption reads "Drinking away rejection. Male [fruit]flies whose attempts at mating have been rejected by females prefer drinking alcohol (right [he does appear comatose, but while on his back he's still guzzling]) over a nonalcoholic sugar drink."
The Times story, explicitly comparative and relatively sober on the subject of addiction and its dynamics, is nonetheless called "Learning from the Spurned and Tipsy Fruit Fly."
It is perhaps apropos to add this intriguing tidbit: Some species of fruit fly, notably Drosophila melanogaster, are engaged in a fascinating and protracted evolutionary battle with tiny, delicate and deadly wasps called parasitoids. In each generation, the wasp evolves to be better and better at finding flies, sinking its eggs in those flies and having the eggs mature into wasps, break out of the fruit fly body, destroying the fly in the process, perhaps feasting on it from the inside on the way. The process sounds a bit ghoulish, out of one of the "Alien" movies, but in fact it is evolutionary cohabitation. The wasp finds her fruitfly hosts, "flies expertly in order to lay her eggs inside the fruitflies as they flee and evade, have an egg-needle just the right length and width to put an egg deep enough but not too deep, and elude the host’s immune system with chemicals and other subterfuge so the hosts immune system does not kill her children. For these reasons, wasps often lay their eggs in just one or a few host species, those with which they have evolved, hosts for which their tools of motherhood are honed."
So it's a kind of evolutionary drama, both death dealing and life giving. If the wasp is successful the host fruit fly dies; if the fruit fly is successful, the wasp larvae die. In successive generations, the wasp evolves to be better and better at finding flies, sinking its eggs in those flies and having the eggs mature into wasps. Each generation, the fruit flies, in turn, evolve counter responses.
Todd Schlenke is a fruit fly biologist at Emory University, and in his neighbor's compost pile. He witnesses this drama again and again, searching to understand and to learn patterns of behavior that might be useful to people as well as the creatures that grow inside us. Todd's curiosity was aroused to find out if alcohol was playing a part. Indeed it was.
Here's the hypothesis: "The flies may be able to use alcohol as a kind of medicine, to kill the wasps once they were infected. This would require the flies to be able to know when they were infected and to respond by drinking more alcohol when they were, even though high levels of alcohol could make them sick too." A delicate business, and one obviously related to our subject above. The experiment is ongoing.
My source for this additional tale is a Scientific American essay with the cute, overly dramatic, potentially misleading and downright silly title "Fruit Flies Use Alcohol to Self-Medicate but Feel Bad About It Afterwards."
Stay tuned.